<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>新增长度单位</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
    .box1{
      width: 200px;
      height: 200px;
      background-color: skyblue;
    }
    .box2{
      width: 50vw;
      height: 20vh;
      margin: 0 auto;
      background-color: green;
    }
  </style>
</head>
<body>
  <div class="box1">像素</div>
  <div class="box2">VW</div>
  
</body>
</html>